Low bandwidth using DPDK2.2 and pktgen-dpdk on ConnectX-3

Hello,

   I'm trying a very simple setup connecting a ConnectX-3 card on one host directly to another ConnectX-3 card on another. I'm using DPDK 2.2 and pktgen-2.9.7 to send packets from one to another. I have configured both sending and receiving ports to Ethernet.

Things are functional, I can saturate 40Gb/s with packet sizes of 1024 or 512 bytes but not with 256 bytes or lower. Seems like the max throughput I get is 12 Mpps.

I verified that I have set log_num_mgm_entry_size=-7.

This is my pktgen command line: pktgen  -c 0xFFF00 -n 4  -w 0000:82:00.0 -m 2048 -- -T -P -p 0x0 -m "[10-11:12-13].0"

Any idea why I can't saturate the line with small packets? Any help would be greatly appreciated.